Systems and methods for providing water for dialysis

Abstract

The water supply system (12) is operable to extract liquid water (EW) from the waste liquid (WF) generated by the dialysis system and provide the liquid water for use by the dialysis system. The water supply system (12) comprises a dehumidifier subsystem (20) and a humidifier subsystem (30). A gas flow circulates between the subsystems (20, 30) and is alternately humidified and dehumidified. The liquid water is extracted from the gas flow by the dehumidifier subsystem (20). The humidifier subsystem (30) comprises a membrane distillation unit (31) having a supply side (31A) and a draw side (31B) separated by a hydrophobic membrane (31'). The waste liquid is supplied to the supply side (31A), the gas flow is supplied to the draw side (31B), and water vapor is transmitted from the waste liquid through the membrane (31') via a partial water vapor pressure difference between the supply side and the draw side (31A, 31B).

Description

Technical Field

[0001] The present disclosure generally relates to dialysis treatment, and more particularly to a technique for providing water for use by a dialysis system when performing dialysis treatment.

Background Art

[0002] Dialysis treatment is performed to replace or supplement the normal blood filtration function of the kidneys. This is used when the kidneys are not functioning adequately, known as renal insufficiency, including acute kidney injury (AKI) and chronic kidney disease (CKD). Dialysis treatment involves the removal of water from the body of a patient suffering from renal insufficiency, as well as the exchange of solutes with the body. An example of dialysis treatment is extracorporeal (EC) blood treatment, in which blood is circulated outside the patient's body and interfaced with one or more medical fluids. Modes of extracorporeal blood treatment include hemodialysis (HD), hemofiltration (HF), and hemodiafiltration (HDF). Another example of dialysis treatment is peritoneal dialysis (PD), in which a medical fluid is injected into the patient's peritoneal cavity to interface with the patient's blood through the peritoneum.

[0003] The medical fluids used in HD and PD are generally known as dialysis fluids. In HF, the medical fluid is known as a replacement fluid because it is injected into the patient's blood to replace the fluid removed during treatment. In HDF, both dialysate and replacement fluid are used.

[0004] Extracorporeal blood treatment by HD, HF, or HDF is performed differently for the treatment of patients with AKI compared to patients with CKD by the use of different types of dialysis devices. Generally, compared to CKD patients, AKI patients are treated continuously at a lower fluid flow rate over a longer period of time. Such continuous treatment is generally known as CRRT (Continuous Renal Replacement Therapy).

[0005] PD may be performed manually or automated. In automated peritoneal dialysis (APD), the dialysis treatment is generally controlled by a machine known as a "cycler". The machine is connected in fluid communication with the peritoneal cavity and is operated to control the flow of fresh dialysis fluid into the peritoneal cavity and the flow of used dialysis fluid out of the peritoneal cavity.

[0006] Over time, dialysis treatment consumes large amounts of medical fluids. In some modalities of dialysis treatment, pre-made medical fluids are delivered to the care location in pre-filled bags (bags filled in advance). For example, conventional PD is performed using pre-filled bags. The AKI machine is configured to use pre-filled bags of medical fluid by installing a pre-filled bag before treatment and replacing the pre-filled bag as needed. On the other hand, CKD machines have an integrated ability to generate medical fluids on demand, so-called online fluid generation, by mixing one or more concentrates with water. Recently, PD machines with the integrated ability of online fluid generation have been proposed.

[0007] Local production of medical fluids at the care location is attractive because it reduces the cost and environmental impact of transporting large quantities of ready-made medical fluids, as well as the burden of storing and handling pre-filled bags. However, the production of medical fluids requires access to purified water. Typically, a water purifier is connected to a municipal water source, and the fluid generation unit is operated to mix one or more concentrates with purified water to produce medical fluids. Large amounts of municipal water may be consumed. In PD, approximately 15 liters of medical fluid are consumed during each treatment session. In EC blood treatment, more than 100 liters of medical fluid can be consumed during a single treatment session. Correspondingly, large amounts of waste fluid are generated in dialysis treatment. The waste fluid may be drained at the care location.

[0008] It is generally necessary to reduce the consumption of municipal water during dialysis treatment.

[0009] There is also a general need to facilitate the installation of a dialysis system configured to generate a medical fluid. Currently, the need for tap water and the need to dispose of waste fluid limit the installation. The tap water source and drain may be located far from the desired location of the dialysis system, requiring significant plumbing work and the use of extended piping, which increases the risk of leaks and resulting water damage.

Summary of the Invention

[0010] An object of the present invention is to at least partially overcome one or more limitations of the prior art.

[0011] One object is to provide a technique for reducing the consumption of tap water by a dialysis system.

[0012] Another object is to facilitate the disposal of waste fluid generated by a dialysis system.

[0013] One or more of these objects, as well as further objects that may become apparent from the following description, are at least partially achieved by a water supply system, an apparatus comprising the water supply system, a computer-implemented method according to independent claims, and a computer-readable medium, embodiments of which are defined by the dependent claims.

[0014] A first aspect is a water supply system for a dialysis system. The water supply system is configured to convert a first gas stream into a second gas stream by extracting liquid water from the first gas stream and to provide the liquid water for use by the dialysis system, a first subsystem; to process the second gas stream by using waste liquid from the dialysis system to generate the first gas stream having an increased humidity compared to the second gas stream, a second subsystem; and a control device configured to operate the first and second subsystems jointly to generate a target amount of the liquid water. The second subsystem includes a membrane distillation (MD) unit defining a supply side and a draw side separated by a hydrophobic membrane. The MD unit is configured to receive the waste liquid at an inlet on the supply side and to receive the second gas stream at an inlet on the draw side. The MD unit is configured to generate the first gas stream by transferring water vapor from the waste liquid through the hydrophobic membrane to the second gas stream via a partial water vapor pressure difference between the supply side and the draw side.

[0015] The water supply system of the first aspect combines gas humidification and gas dehumidification to generate liquid water for use by a dialysis system. The first aspect is based on the insight that by performing the gas humidification in the water supply system by membrane distillation, it is possible to utilize the waste liquid generated by the dialysis system. Such a water supply system can be operated to recycle at least a portion of the water in the waste liquid and would reduce the need to supply tap water to operate the dialysis system. Further, since the membrane distillation removes water vapor from the waste liquid, the waste liquid thus treated has a reduced volume, facilitating its disposal. It is understood that the water supply system of the first aspect can significantly facilitate the handling of the dialysis system and can facilitate its installation by reducing or eliminating the need for piping between the tap water source and / or drain and the dialysis system and / or the water supply system.

[0016] In some embodiments, the control device is configured to selectively operate the first subsystem to obtain at least a portion of the first gas stream from ambient air and supply at least a portion of the second gas stream to the ambient air.

[0017] In some embodiments, the control device is configured to selectively switch the system between a first mode in which the system is configured to transfer the first and second gas streams between the first and second subsystems in a closed loop, and a second mode in which the transfer is blocked and the first subsystem is operated to obtain the first gas stream from the ambient air and provide the second gas stream to the ambient air.

[0018] In some embodiments, the control device is configured to switch between the first and second modes based on at least one of the current moisture content of the ambient air, the availability of the waste liquid, the availability of liquid water, or a time schedule.

[0019] In some embodiments, the second subsystem further comprises a heating device disposed upstream of the inlet on the supply side of the MD unit and operable to heat the waste liquid.

[0020] In some embodiments, the heating device comprises a heat transfer device configured to transfer thermal energy from the first gas stream generated by the MD unit to the waste liquid.

[0021] In some embodiments, the second subsystem further comprises a WF sensor disposed downstream of the outlet on the supply side of the MD unit to provide a measurement signal indicative of a concentration-related characteristic of the waste liquid, and the control device is configured to operate the second subsystem based on the measurement signal.

[0022] In some embodiments, the concentration-related characteristics include concentration, density, conductivity, color, transparency, or refractive index.

[0023] In some embodiments, the second subsystem defines a recirculation path including the supply side of the MD unit, the second subsystem includes a pump device in the recirculation path, and the control device is configured to operate the pump device based on the measurement signal to recirculate the waste liquid through the supply side of the MD unit.

[0024] In some embodiments, the control device is further configured to selectively operate a first flow controller that introduces a first amount of waste liquid into the recirculation path and a second flow controller that discharges a second amount of treated waste liquid from the recirculation path, and the treated waste liquid includes waste liquid that has been recirculated at least once through the supply side of the MD unit.

[0025] In some embodiments, the control device is configured to sequentially operate the first flow controller to introduce the first amount into the recirculation path, operate the pump device to circulate at least the first amount through the supply side of the MD unit, and operate the second flow controller to discharge the second amount from the recirculation path.

[0026] In some embodiments, the control device is configured to simultaneously operate the first flow controller to introduce the first amount into the recirculation path and the second flow controller to discharge the second amount from the recirculation path such that the difference between the first and second amounts is substantially equal to a third amount of water transferred through the hydrophobic membrane into the second gas stream.

[0027] In some embodiments, the control device is configured to selectively operate a supply device to supply tap water to the recirculation path and operate the pump device to circulate the tap water through the supply side of the MD unit.

[0028] In some embodiments, the water supply system further comprises an EW container configured to receive the liquid water from the first subsystem, and the control device is configured to operate the first and second subsystems according to the filling level of the EW container indicated by a level sensor associated with the EW container.

[0029] In some embodiments, the water supply system further comprises a WF container arranged for intermediate storage of the waste liquid and fluidly connected to the inlet on the supply side of the MD unit.

[0030] In some embodiments, the WF container is associated with a sterilization device operable to sterilize the WF container.

[0031] In some embodiments, the first and second gas flows include air.

[0032] In some embodiments, the control device is configured to determine a first setting of the first subsystem to achieve the target amount and to determine a second setting of the second subsystem based on the first setting, the second setting defining the moisture content and flow rate of the first gas flow generated by the second subsystem.

[0033] In some embodiments, the first subsystem is arranged to adsorb and / or absorb moisture from the first gas flow and comprises the desiccant, which is processed by the first subsystem to extract the liquid water from the desiccant.

[0034] In some embodiments, the desiccant is configured to have a high selectivity for water.

[0035] In some embodiments, the liquid water extracted from the first gas flow has a conductivity of less than 10 μS / cm, preferably less than 5 μS / cm or 1 μS / cm.

[0036] In some embodiments, the first subsystem comprises a cooling element configured to cool the first gas stream to extract the liquid water from the first gas stream by condensation.

[0037] A second aspect is a configuration comprising a water supply device of the first aspect, or any embodiment thereof, and the dialysis system configured to receive a medical fluid for use in a dialysis treatment performed by the dialysis system and to generate a waste liquid that is at least partially generated from the medical fluid during the dialysis treatment, wherein the dialysis system is fluidly connected to transmit the waste liquid to the water supply system.

[0038] In some embodiments, the dialysis system comprises a fluid preparation subsystem configured to receive at least a portion of the liquid water provided by the water supply system and to generate the medical fluid by mixing the at least a portion of the liquid water with one or more concentrates.

[0039] In some embodiments, the dialysis system is configured to generate a portion of the waste liquid during a cleaning operation of the dialysis system, and the dialysis system is configured to perform the cleaning operation by using a portion of the liquid water provided by the water supply system.

[0040] A third aspect is a computer-implemented method for providing water for use by a dialysis system. The method includes operating a first subsystem that converts the first gas stream into a second gas stream by extracting liquid water from the first gas stream, providing liquid water for use by the dialysis system, and operating a second subsystem in cooperation with the first subsystem to process the second gas stream by using waste liquid from the dialysis system and generate the first gas stream having an increased humidity compared to the second gas stream. Operating the second subsystem includes supplying the waste liquid at an inlet on a supply side of a membrane distillation (MD) unit and supplying the second gas stream at an inlet on a draw side of the MD unit, the draw side being separated from the supply side by a hydrophobic membrane, and the MD unit being configured to generate the first gas stream by transferring water vapor from the waste liquid through the hydrophobic membrane to the second gas stream via a partial vapor pressure difference between the supply side and the draw side.

[0041] Embodiments of the first aspect can be adapted as embodiments of the third aspect.

[0042] A fourth aspect is a computer-readable medium including program instructions that, when executed by a processing circuit, cause the processing circuit to execute the method of the second aspect or any embodiment thereof. The computer-readable medium can be a non-transitory medium or a propagated signal.

[0043] Still other objects, aspects, embodiments, and technical effects, as well as features and advantages, may become apparent from the following detailed description, the appended claims, and the drawings.

Brief Description of the Drawings

[0044]

Figure 1A

Figure 1B

Figure 1C

Figure 2

Figure 3A

Figure 3B

Figure 4

Figure 5A

Figure 5B

DETAILED DESCRIPTION OF THE INVENTION

[0045] List of Abbreviations DH Dehumidification DHU Dehumidifier DIA Inlet airflow DOA Outlet airflow EIA Inlet ambient air EOA Outlet ambient air EC Extracorporeal EW Extracted liquid water FWF Final waste liquid HD Hemodialysis HDH Humidification-dehumidification Hdi Inlet humidity HDF Hemodiafiltration Hdo Outlet humidity HF Hemofiltration HU Humidifier MD Membrane distillation MF Medical fluid MOF Metal-organic framework PC Peritoneal cavity PD Peritoneal dialysis RH Relative humidity TW Tap water WF Waste liquid WSS Water supply system

[0046] Reference will now be made to the accompanying drawings, which show, for purposes of illustration, some, but not all, embodiments of the disclosure. In fact, the subject matter of the present disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements.

[0047] Also, to the extent possible, any advantages, features, functions, devices, and / or operational aspects of any of the embodiments described and / or contemplated herein can be included in any of the other embodiments described and / or contemplated herein, and / or vice versa. Further, to the extent possible, any term expressed in the singular herein is meant to also include the plural and / or vice versa, unless explicitly stated otherwise. As used herein, "at least one" means "one or more" and these phrases are intended to be interchangeable. Thus, the terms "a" and / or "an" are meant to mean "at least one" or "one or more," although the phrase "one or more" or "at least one" may also be used herein. As used herein, the words "comprise," "comprises," "comprising," and the like, unless the context dictates otherwise, are used in an inclusive sense, i.e., to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments.

[0048] As used herein, the terms "multiple," "plural," and "plurality" are intended to mean the provision of two or more elements, whereas the term "set" of elements is intended to mean the provision of one or more elements. The term "and / or" includes any and all combinations of one or more of the associated listed elements.

[0049] Furthermore, terms such as first, second, etc. may be used in this specification to describe various elements, but it should be understood that these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of the present disclosure, the first element may be referred to as the second element, and similarly, the second element may be referred to as the first element.

[0050] Well-known functions or configurations may not be described in detail for the sake of brevity and / or clarity. Unless otherwise defined, all terms (including technical and scientific terms) used in this specification have the same meaning as commonly understood by those skilled in the technical field to which this disclosure belongs.

[0051] As used herein, "dialysis treatment" refers to any treatment that replaces or supplements a patient's kidney function by the use of medical fluids. Dialysis treatments include, but are not limited to, extracorporeal blood treatment and peritoneal dialysis treatment.

[0052] As used herein, "medical fluid" refers to any fluid consumed as a result of dialysis treatment. Medical fluids include, but are not limited to, dialysis fluid for injection into the peritoneal cavity during peritoneal dialysis treatment, dialysis fluid for supply to a dialyzer during EC blood treatment, replacement fluid and alternative fluid for injection into the blood during EC blood treatment, priming fluid, and fluid for disinfection and / or cleaning of the dialysis system.

[0053] As used herein, "sterilization" refers to any process that substantially removes, kills, or inactivates microorganisms and other biological agents. In the context of the present disclosure, sterilization, disinfection, and sanitization are not distinguished. Sterilization may include applying one or more of heat, chemicals, irradiation, high pressure, or filtration.

[0054] As used herein, "purification" refers to the process of substantially removing undesirable chemical substances, biological contaminants, suspended solids, and gases from water for the purpose of providing water having a purity acceptable for use in medical fluids.

[0055] As used herein, "priming" refers to the process of removing air and / or possible fragments of residual sterilant or other residues from the fluid path within a dialysis system prior to the start of a treatment session. Priming includes flushing the fluid path with a liquid that is compatible with humans.

[0056] As used herein, "tap water" refers to water provided through a water supply valve ("water tap, faucet") connected to indoor plumbing. Tap water, also known as faucet water, running water, or municipal water, is commonly used for drinking, cooking, washing, and toilet flushing.

[0057] Like reference numerals refer to like elements throughout.

[0058] The present disclosure relates to techniques for providing water for use in dialysis systems. This technique is applicable to any type of dialysis system, including systems for peritoneal dialysis (PD) treatment or extracorporeal (EC) blood treatment. Merely for context, the use of water in relation to PD treatment and EC blood treatment is briefly illustrated and discussed with reference to FIGS. 1A - 1B.

[0059] Figure 1A is a general schematic of a system for PD treatment. The system comprises a dialysis system 10 that is fluidly connected to the peritoneal cavity (PC) of a patient P. As indicated by the double-headed arrow, the dialysis system 10 is operable to carry fresh dialysis fluid into the PC and receive used dialysis fluid from the PC on fluid path 11. The fluid path 11 may be defined by a tube that connects to an implanted catheter (not shown) in fluid communication with the PC. The dialysis system 10 may be configured for any type of PD treatment. In one example, the dialysis system 10 comprises a dialysis machine (“cycler”) that performs the dialysis treatment. The dialysis system 10 is fluidly connected to receive water from a water supply system (WSS) 12 on a first fluid path 13A and supply waste fluid to the WSS 12 on a second fluid path 13B. In the embodiments described below, the waste fluid is used by the WSS 12 to produce water. The water supplied by the WSS 12 can be used by the dialysis system 10 to produce dialysis fluid by mixing the water with one or more concentrates. The water may also be used for maintenance operations such as cleaning (rinsing), sterilizing, or priming the dialysis system 10. For example, the dialysis system 10 may be configured to produce a dedicated maintenance fluid for each maintenance operation by using water from the WSS 12. Alternatively, such maintenance fluid may be supplied from a separate source, e.g., a pre-filled bag.

[0060] Figure 1B is a general schematic of a system for EC blood treatment. WSS12 may be the same as in Figure 1A. The dialysis system 10 is fluidly connected to the patient P's vasculature on the fluid path. In the illustrated example, the fluid path includes a tube 11A for blood extraction and a tube 11B for blood return. As indicated by the arrows, the dialysis system 10 is operable to draw blood from the patient P through the tube 11A, process the blood, and return the processed blood to the patient through the tube 11B. Each tube 11A, 11B is connected to an access device (e.g., a catheter, graft, or fistula (fistula opening), not shown) that is in fluid communication with the patient P's vasculature. The dialysis system 10 may be configured to process blood by any modality of EC blood treatment such as HD, HF, or HDF. Depending on the modality, dialysis fluid and / or replacement fluid is consumed during such treatment. The dialysis system 10 may be configured to generate dialysis fluid and / or replacement fluid, if necessary, by mixing purified water with one or more concentrates. The dialysis system 10 is fluidly connected to receive water from WSS12 on the first fluid path 13A and supply waste liquid to WSS12 on the second fluid path 13B. Similar to Figure 1A, the dialysis system 10 can also generate maintenance fluid by using water from WSS12.

[0061] Figure 1C is a more detailed view of a system including dialysis system 10 and WSS 12. Dialysis system 10 includes a preparation subsystem 14 and a treatment subsystem 16. Treatment subsystem 16 is configured to receive a medical fluid (MF) and perform a dialysis treatment using the MF. It is understood that treatment subsystem 16 is configured to perform a specific type of dialysis treatment such as PD treatment or EC blood treatment of any modality. Also, it is understood that the MF may be a dialysis fluid or a replacement fluid, or a combination thereof, depending on the dialysis treatment. During the dialysis treatment, treatment subsystem 16 generates a waste fluid (WF) including waste, toxins, and excess water from the patient. When a dialysis fluid is used in the dialysis treatment, the waste fluid includes a used dialysis fluid, also known as a "spent dialysis fluid" including at least a portion of the waste, toxins, and excess water. The waste fluid may also include MF that was discarded without being used, as well as a maintenance fluid used in a maintenance operation ("used maintenance fluid").

[0062] Preparation subsystem 14 includes a mixing device 40 configured to mix water with one or more concentrates (CCx) to produce a medical fluid (MF). The MF may be produced by preparation subsystem 14 in batches or on demand. Here, "on demand" means that the MF production rate matches the MF consumption rate in treatment subsystem 16. Each concentrate may be in liquid or powder form. Mixing devices for MF production are well known in the art and need not be described in detail herein. It should be understood that preparation subsystem 14 can include any combination of conventional components for temperature adjustment, degassing, etc. As shown by the arrows in Figure 1C, fluid preparation subsystem 14 may also output WF, which may include used maintenance fluid and discarded MF.

[0063] As shown in FIG. 1C, the WSS 12 is configured to receive WF from the dialysis system 10 and process the WF for extraction of liquid water shown as EW. The WSS 12 is configured to provide the EW to the preparation subsystem 14 for use in generating MF and optional maintenance fluid. The WF processing results in a final waste fluid (FWF), which is output from the WSS 12 for disposal. As shown, the WSS 12 can also receive tap water (TW) for use in EW generation. The WSS 12 comprises a combination of a dehumidifier (DHU) subsystem 20 and a humidifier (HU) subsystem 30, which operate jointly to extract EW from the WF. As will be described in more detail below, the HU subsystem 30 utilizes membrane distillation (MD) to humidify a gas using the waste fluid. The gas humidified in this way is conveyed to the DHU subsystem 20 configured to generate EW from the humidified gas. In other words, the gas is utilized as a medium for transferring water vapor from the HU subsystem 30 to the DHU subsystem 20. Typically, most of the WF is water, which is available for extraction by MD. Thereby, the WSS 12 can generate water for the dialysis system 10 with minimal or no use of tap water.

[0064] Membrane distillation is a separation process driven by a phase change. A hydrophobic membrane (MD membrane) provides a barrier to the liquid phase that allows the vapor phase to pass through the pores of the MD membrane. The driving force for the separation process is the difference in partial vapor pressure across the MD membrane, which is generally known as the feed side and the draw side (or permeate side), respectively. In the HU subsystem 30, the waste liquid is provided to the feed side and the gas is provided to the draw side. By controlling the difference in partial water vapor pressure between the feed side and the draw side, water vapor is transferred from the waste liquid through the MD membrane into the gas. By properly designing the MD membrane, all non-volatile substances such as salts can be effectively retained on the feed side. The gas is driven to flow through the MD membrane on the draw side, thereby increasing the amount of water that can be transferred through the MD membrane per unit time. This type of MD technique is known in the art as sweeping gas MD (SWGMD).

[0065] The water vapor separation in the HU subsystem 30 reduces the residual volume of the waste liquid to be treated as a result of the treatment session shown by FWF in FIG. 1C. For example, the volume ratio of FWF to WF may range from 0.1 to 0.5. The reduced need for tap water and the small volume of FWF have the potential to facilitate installation. For example, the need for a permanent fluid connection between the WSS12 and the water supply can be eliminated. Any required tap water can be easily manually supplied to the WSS12 by the user. Similarly, the need for a permanent fluid connection to the drain may not be necessary. For example, the FWF may be collected in a container that is manually emptied by the user.

[0066] The mobility of the dialysis system can also be increased by reducing the amount of fluid that needs to be transmitted along with the dialysis system to enable its operation through the use of WSS as described herein. In addition to the concentrate used by the dialysis system, if the WSS is operable to extract water from the waste fluid generated by the dialysis system, only a portion of the total amount of water consumed during a treatment session can be transmitted, in addition to the concentrate used by the dialysis system.

[0067] Depending on the implementation, the water extracted by the DHU subsystem 20 can have a purity sufficient to comply with the quality requirements of the water contained in the medical fluid, for example, in accordance with ISO 23500-3. If not, the WSS 12 and / or the dialysis system 10 may include a dedicated purification device for treating the water from the DHU subsystem 20 before it is used by the mixing device 40. The dedicated purification device can apply any conventional water purification technology to meet the above-mentioned quality requirements. It should also be understood that the WSS 12 and / or the dialysis system 10 may include a sterilization device to ensure that the medical fluid complies with the microbial requirements, for example, in accordance with ISO 23500-3 as described above.

[0068] FIG. 2 is a block diagram of an exemplary WSS 12 including a HU subsystem 30 and a DHU subsystem 20. In the illustrated example, the HU subsystem 30 is fluidly connected to the DHU subsystem 20 to form a closed gas loop, and the humidified gas (DIA) generated by the HU subsystem 30 is supplied to the DHU subsystem 20 for dehumidification. As a result, the extracted water (EW) and the dehumidified gas (DOA) are obtained, which are supplied to the subsystem 30 for humidification, and the humidified gas (DIA) is obtained again. The gas is driven to circulate within the closed loop by a pumping device (not shown).

[0069] The control device 60 (the "main controller") is configured to operate the subsystems 20, 30 jointly to generate a target amount of EW. The target amount can be defined as the specified flow rate of EW, the specified amount of EW over a specified period, or the specified or unspecified amount of EW generated when the subsystems 20, 30 operate at maximum capacity. The main controller 60 is configured to indicate the operation of the WSS12, receive a measurement signal represented as Si, control the operation of the WSS12, and provide a control signal represented as Cj. The WSS12 may or may not include a subcontroller that operates under the control of the main controller 60. For example, the DHU subsystem 20 can include a local controller (209 in FIG. 4) configured to control the operation of the DHU subsystem 20 according to a control signal C3 from the main controller 60. Similarly, the HU subsystem 30 can include a corresponding local controller (39 in FIGS. 5A - 5B). The main controller 60 may be configured to generate the control signal Cj according to a control program including computer instructions. The main controller 60 includes a circuit including one or more processors 61 and a computer memory 62. The control program may be stored in the memory 62 and executed by the processor 61. The control program can be supplied to the main controller 60 on a computer-readable medium, which can be a tangible (non-transitory) product (e.g., magnetic medium, optical disk, read-only memory, flash memory, etc.) or a propagated signal. In the illustrated example, the main controller 60 includes a signal interface 63 for the input of the signal Si and the output of the signal Cj.

[0070] The HU subsystem 30 includes a membrane distillation (MD) unit 31. The MD unit 31 includes a supply side 31A and a draw side 31B separated by an MD membrane 31'. The different sides may also be referred to as compartments. The membrane 31' is a hydrophobic microporous membrane and can be configured according to established knowledge, for example, as described in the article "Membrane distillation: A comprehensive review" by Alkhudiri et al. in Desalination, vol. 287, pp2 - 18 (2012). The geometric shape of the membrane 31' may be a flat sheet (plate-like), tubular, or hollow fiber. The MD unit 31 is configured to carry a liquid fluid to the supply side 31A and a gas fluid to the draw side 31B. The fluid flow is usually countercurrent (opposite flow) within the MD unit 31, as indicated by the arrows, but may alternatively be co-current. The flow of each fluid through the MD unit 31 may be continuous or intermittent. In some embodiments illustrated in FIG. 2, the waste liquid passes through the supply side 31A only once ("single pass configuration"). In other embodiments illustrated in FIGS. 6A - 6B and further described below, the waste liquid is recycled through the supply side 31A at least once ("multi-pass configuration"). As used herein, "recycled at least once" means that the waste liquid passes through the MD unit 31 at least twice.

[0071] The MD unit 31 includes at least one input port 31Ai (one is shown) and at least one output port 31Ao (one is shown) on the supply side 31A, and at least one input port 31Bi (one is shown) and at least one output port 31Bo (one is shown) on the extraction side 31B. The MD unit 31 is configured to receive the waste liquid WF through the input port 31Ai on the supply side 31a and receive the gas DOA through the input port 31Bi on the extraction side 31B. As understood from the above, water vapor is transmitted from the WF to the gas through the membrane 31', resulting in the generation of the humidified gas DIA, which exits from the extraction side 31B through the outlet port 31Bo. The inflowing waste liquid becomes more concentrated by the MD treatment. In the illustrated example having a single-pass configuration, the waste liquid exiting from the supply side 31A through the outlet port 31Ao forms the final waste liquid FWF provided for disposal.

[0072] The HU subsystem 30 further includes a pump P1 for driving the flow of the waste liquid WF through the supply side 31A. In the illustrated example, the pump P1 is arranged upstream of the input port 31Ai, but alternatively or additionally, it may be arranged downstream of the output port 31Ao.

[0073] In the illustrated example, the HU subsystem 30 further includes a heating device 32 arranged upstream of the input port 31Ai. The heating device 32 is operable to heat the waste liquid before it enters the supply side 31A. The heating increases the partial pressure of water vapor on the supply side 31A, thereby promoting the transmission of water vapor through the membrane 31'. The heating device 32 can include an electric heater. Although not shown in FIG. 2, the heating device 32 can further include a temperature sensor downstream of the electric heater to provide temperature feedback for controlled heating.

[0074] In the illustrated example, the HU subsystem 30 further includes a "WF sensor" 33 disposed downstream of the outlet port 31Ao. The WF sensor 33 is operable to measure concentration-related characteristics of the waste liquid exiting from the supply side 31A of the MD unit 31 and provide a corresponding measurement signal S1. The concentration-related characteristics correlate with or represent the concentration of one or more substances in the waste liquid and thus indicate water transfer within the MD unit 31. The WF sensor 33 may be configured to provide relative or absolute measurement values. In one embodiment, the WF sensor 33 is a concentration sensor configured to measure, for example, sodium concentration, or a conductivity sensor. In another embodiment, the WF sensor 33 is configured to measure density. In one example, the density is determined by measuring the weight of a predetermined volume of waste liquid exiting the MD unit 31. In another embodiment, the WF sensor 33 is configured to measure the color, transparency, or refractive index of the waste liquid.

[0075] The operation of the HU subsystem 30 is controlled by the main controller 60, optionally via a local controller (see 39 in FIGS. 5A - 5B) within the HU subsystem 30. As shown, the HU subsystem 30 is at least partially controlled by a control signal C1 for the pump P1 and a control signal C2 for the heating device 32 (if present). The control signals C1, C2 can be generated at least partially based on the signal S1 from the WF sensor 33. The operation of the DHU subsystem 20 is similarly controlled by the main controller 60 by one or more control signals. In FIG. 2, it is assumed that the DHU subsystem 20 includes a local controller that operates based on a control signal C3 from the main controller 60.

[0076] In FIG. 2, the WSS 12 includes a first container 51 (the "WF container") that is fluidly connected to receive waste liquid from the dialysis system. The WF container 51 is configured to hold an intermediate supply of waste liquid used by the HU subsystem 30. For this purpose, the WF container 51 is fluidly connected to the inlet port 31Ai. By providing the WF container 51, the operation of the HU subsystem 30 is decoupled from the generation of waste liquid by the dialysis system. For example, WF can be accumulated in the container 51 during a treatment session for later use during the same or a different treatment session. The WF container 51 can be configured as a permanent part of the WSS 12 or as a disposable unit that is discarded after a predetermined time after installation or after a predetermined number of treatment sessions. In the illustrated example, a sterilizer 51' is associated with the WF container 51. The sterilizer 51' is selectively operable by the main controller 60 to sterilize the internal compartment of the container 51 and / or the waste liquid therein. The sterilizer 51' is configured to use any suitable sterilization technique such as the application of heat or radiation (e.g., UV radiation). Alternatively or additionally, the walls of the internal compartment of the container 51 may be lined with an antibacterial material, such as a plastic material.

[0077] Although not shown in FIG. 2, the WSS 12 may include two or more WF containers 51, for example, one container for holding high-concentration waste liquid such as used medical fluid or discarded medical fluid, and one container for holding low-concentration waste liquid such as cleaning fluid or priming fluid. The WSS 12 may be selectively operable, for example, by a suitable valve device (not shown), to fluidly connect any one of the WF containers to the inlet port 31Ai.

[0078] In FIG. 2, the WSS 12 includes a second container 52 (the "EW container") configured to receive EW from the DHU subsystem 20. The EW container 52 is configured to hold an intermediate source of EW used by the dialysis system. Thereby, the EW container 52 decouples the operation of the DHU subsystem 20 from the water consumption by the dialysis system. The EW container 52 may be a permanent component or a disposable unit. In the illustrated example, a level sensor 52' is provided to indicate the amount of liquid water in the EW container 52. In some embodiments, the main controller 60 is configured to operate the subsystems 20, 30 according to the filling level of the reservoir 52. For example, the subsystems 20, 30 may be controlled to ensure that the amount of water in the EW container 52 exceeds a minimum level. The minimum level may be fixed or may vary over time, for example, during the course of a treatment session.

[0079] In FIG. 2, the WSS 12 includes a third container (the "TW container") 53 fluidly connected to the inlet port 31Ai and configured to supply tap water to the supply side 31A of the MD unit 31 separately from or together with the WF. The WSS 12 may be operated to supply TW from the TW container 53 to supplement the WF, for example, when the available amount of WF in the WF container 51 is considered insufficient in view of the EW generation target. Thus, tap water is used only occasionally, and the TW container 53 may be manually filled with tap water by the user.

[0080] Although not shown in FIG. 2, the EW container 52 and / or the TW container 53 may each include a respective sterilization device and / or be lined internally with an antibacterial material, similar to the WF container 51. Further, similar to the level sensor 52' of the EW container 52, respective level sensors may be provided to indicate the amount of fluid in the WF container 51 and / or the TW container 53.

[0081] In FIG. 2, the WSS12 further includes valve devices represented by first and second valves V', V'' upstream and downstream of the DHU subsystem 20, respectively. The valve devices are operable to switch the WSS12 between an HDH mode (humidification - dehumidification) and a DH mode (dehumidification).

[0082] In the HDH mode, as indicated by the solid - line arrows, the DHU subsystem 20 is fluidly connected to the HU subsystem 30 in a closed loop, so that the same gas is alternately and repeatedly humidified in the HU subsystem 30 and dehumidified in the DHU subsystem 20. As a result, water vapor is extracted from the WF in the MD unit 31 and materializes as liquid water in the DHU subsystem 20.

[0083] In the DH mode, the DHU subsystem 20 is fluidly separated from the HU subsystem 30 and instead is operated to receive and dehumidify "ambient air", i.e., air EIA from the surroundings. The dehumidified air EOA is output to the surroundings. Thus, in the DH mode, DIA is equal to EIA and DOA is equal to EOA. In the DH mode, the subsystem 30 may be deactivated, for example, by turning off the pump P1 and the heating device 32 in order to save power.

[0084] In FIG. 2, each valve V', V'' is a three - way valve operable to selectively open different passages in response to control signals C4a, C4b generated by the main controller 60 or the local controller 209 of FIG. 4. The valve configuration of FIG. 2 is merely an example, and many alternative configurations are available to those skilled in the art.

[0085] The DH mode is optional, but may be used, for example, to supplement water extraction from the waste liquid when WF is insufficient or when the water extracted from the WF is considered insufficient to meet the needs of the dialysis system.

[0086] It is also conceivable to operate the WSS12 to circulate gas between the subsystems 20, 30 by combining the HDH mode and the DH mode, and to pass ambient air through the DHU subsystem 20 for dehumidification. In such a combination, the circulating gas is air, and a portion of this air is refreshed by the air exchange represented by the EIA and EOA in FIG. 2. In other words, the EIA forms part of the DIA, and the EOA forms part of the DOA. However, volatile substances in the WF can pass through the membrane 31'. When such volatile substances are released into the surroundings, an unpleasant or at least unfamiliar odor can be experienced by the user. For at least this reason, an exclusive switch between the HDH mode and the DH mode is currently considered to be a better option.

[0087] FIG. 3A is a flowchart of a method 300 for operating the WSS12 in the HDH mode. The method 300 includes steps 301-304 described with reference to the WSS12 of FIG. 2.

[0088] In step 301, waste liquid is received from the dialysis system. Step 301 can be executed whenever WF is generated by the dialysis system (every time it is generated). In the example of FIG. 2, the incoming WF is accumulated in the container 51.

[0089] Steps 302 and 303 are executed simultaneously by circulating gas within the closed loop between subsystems 20 and 30 (solid arrows in FIG. 2). In step 302, the DHU subsystem 20 is operated to convert the first gas stream into a second gas stream by extracting liquid water (EW) from the first gas stream. In FIG. 2, step 302 includes dehumidifying the incoming humid gas stream (DIA) to produce an outgoing dehumidified gas stream (DOA). In step 303, the HU subsystem 30 is operated to process the second gas stream produced by the DHU subsystem 20 and increase its humidity by using waste liquid. Thereby, the second gas stream forms the first gas stream that is output for receipt by the DHU subsystem 20. In FIG. 2, step 303 includes humidifying the incoming gas stream to convert the dehumidified gas stream (DOA) into a humidified gas stream (DIA).

[0090] As understood from the exemplary structure of FIG. 2, step 303 includes the use of the MD unit 31. As a result, as shown in FIG. 3A, step 303 includes step 303A of supplying WF at the inlet 31Ai of the supply side 31A of the MD unit 31 and step 303B of supplying the second gas stream (DOA) at the inlet 31Bi of the extraction side 31B of the MD unit 31.

[0091] In step 304, EW is provided for use by the dialysis system. Step 304 can be executed whenever water is required by the dialysis system. In the example of FIG. 2, EW is supplied from the EW container 52, in which EW accumulates during operation of the DHU subsystem 20.

[0092] In the example of FIG. 2, steps 302 and 303 are performed by main controller 60 that controls the operation of subsystems 20, 30 with control signals C1, C2, C3, C4a, C4b generated at least in part based on measurement signal S1. Steps 301 and 304 may be performed by main controller 60 or a separate controller of the dialysis system.

[0093] If WSS12 is configured to operate only in the HDH mode where gas is confined within a closed fluid circuit, the gas circulated between subsystems 20, 30 can be selected to optimize DHU-HU performance. However, if WSS12 is operable, for example, to process ambient air in the DH mode, then WSS12 circulates air through subsystems 20, 30 in the HDH mode. For practical reasons, it may be advantageous to circulate air even if WSS12 is configured to operate only in the HDH mode.

[0094] FIG. 3B is a flowchart of control procedure 310 that may be performed by main controller 60 to selectively set WSS12 to the HDH mode or the DH mode. In step 311, WSS12 is operated in the HDH mode, which is the default mode. In step 312, a first switch condition for switching WSS12 to the DH mode is detected. Then, when WSS12 is operating in the DH mode, according to step 313, a second switch condition is detected in step 314 to switch WSS12 back to the HDH mode. As indicated by the arrow from step 314 to step 311, WSS12 can be switched back and forth between the HDH mode and the DH mode any number of times (any number of times) during operation.

[0095] The switching between modes can be pre-scheduled. Thus, the first and second switch conditions can be given by the time point of the time schedule. For example, the pre-scheduling can be based on user preferences or consideration of noise. It should be understood that the DH mode is likely to generate more noise than the HDH mode as a result of the air exchange with the surroundings. For example, when the WSS12 is located within the user's site, it may not be desirable to operate the WSS12 in the DH mode at night. The switching may also be performed dynamically based on the sensed characteristics of the WSS12 or its surroundings. For example, the switch (transition) from the HDH mode to the DH mode can be triggered by the insufficient availability of the WF (step 311). In FIG. 2, the availability of the WF may be given by the amount of WF in the WF container 51. Conversely, when the availability of the WF becomes sufficient again, the switch (transition) from the DH mode to the HDH mode can be triggered (step 314). In another example, the switching can be triggered based on the amount of moisture in the ambient air, represented by, for example, the relative humidity (RH) measured by the WSS12 (see sensors 204, 206 in FIG. 4 below). For example, to maintain an acceptable humidity within the site of the WSS12, when the humidity falls below the upper limit value, the switch from the DH mode to the HDH mode may be triggered (step 314). Conversely, the switch from the HDH mode to the DH mode can be triggered when the amount of available water in the ambient air exceeds a further upper limit value (step 312). The amount of water can optionally be given by the RH, estimated by the WSS12, or input by the user, in combination with the room size. In a further example, the switch in step 312 and / or step 314 can be performed (pre-scheduled or dynamically) based on historical data representing the operation of the WSS12, the tendency of membrane fouling in the MD unit 31, etc.

[0096] By providing the WF container 51, it is possible to store WF for later use even if not all WF is processed into EW during the dialysis session. For example, if the dialysis session is performed at night, at least a portion of the WF is saved and, after treatment, can be processed for water extraction during the day. Thus, it is not necessary to process all of the WF generated during the dialysis session during this dialysis session.

[0097] To reduce the drying effect on the ambient air and also to increase the amount of water extracted by the DHU subsystem 20, it may be beneficial to spread the operation of the WSS12 in the DH mode over the course of a day. When the WSS12 operates in the HDH mode for an extended period, a significant amount of the available water in the ambient air is not used and could potentially be ventilated from within the site (building). By intermittently switching to the DH mode, the moisture in the ambient air can be utilized without significantly affecting the humidity of the surrounding air. By using the DH mode for shorter periods and activating the HDH mode in between, it becomes possible to restore the humidity of the surrounding air.

[0098] Returning to Fig. 3A, it can be seen that step 303 may include an optional step 303C of selectively introducing tap water (TW) into the inlet 31Ai of the supply side 31A of the MD unit 31. TW may enter through the same inlet as WF or through a separate inlet, as shown in Fig. 2. Step 303C may be performed based on the availability of WF and / or EW with respect to the actual or anticipated EW consumption by the dialysis system. By providing TW to the supply side 31A, TW is seamlessly introduced into the existing water extraction process performed by the subsystems 20, 30 and will essentially undergo the same extraction process as WF. In some embodiments, the WSS 12 is operated to mix TW with WF before WF enters the supply side 31A or before entering the interior of the MD unit 31. In other embodiments, the WSS 12 is operated to alternately supply TW and WF to the supply side 31A of the MD unit 31. Step 303C may be performed for reasons other than increasing the amount of EW, for example, to reduce membrane fouling. Membrane fouling results in a decrease in membrane performance due to the accumulation of substances on the surface and / or within the pores of the membrane 31'. Step 303C can reduce membrane fouling by diluting WF and / or rinsing the membrane 31'.

[0099] The usefulness of the water extraction technique described in this specification is further illustrated in relation to non-limiting numerical examples for PD treatment. Generally, the total WF amount available for water extraction correlates with the amount of water extracted if all of the extracted water is supplied to the dialysis system and ultimately becomes WF. In the numerical example, it is assumed that 13.5 L (liters) of dialysate is consumed during a PD session, and the dialysate is produced by mixing a liquid concentrate and water at a volume ratio of 1:12.5. Thus, 12.5 L of water is consumed to produce the dialysate. Assuming that 1 L of ultrafiltrate is extracted from the patient during the PD session, the resulting amount of used dialysate is 14.5 L. Further, 3.5 L of water (for rinsing, disinfection, etc.) is used as maintenance fluid, and as a result, the used maintenance fluid is 3.5 L. Assuming that 75% of the water in the used dialysate and 90% of the used maintenance fluid are extracted by operating WSS12 in the HDH mode, the amount of water extracted from the waste liquid (used dialysate and used maintenance fluid) is 0.75×14.5 + 0.9×3.5 ≒ 14 L. The required amount of water is 12.5 + 3.5 = 16 L. Thus, in this numerical example, 14 L of the required 16 L of water is extracted from the waste liquid. The remaining 2 L of water may be generated by pure extraction of water from the ambient air by operating WSS12 in the DH mode and / or supplied to WSS12 as tap water. Accordingly, the main controller 60 may be configured to control the overall operation of WSS12 so as to achieve a daily EW target value of 16 L.

[0100] It is understood that WSS12 significantly reduces or even eliminates the need to supply tap water before each treatment session performed by the dialysis system. The supply of fresh tap water may be carried out before the first treatment session of a series of treatment sessions, and then it should be noted that water is extracted from the waste liquid of each subsequent treatment session and used in this treatment session and / or subsequent treatment sessions. Alternatively, WSS12 may be operated in DH mode to extract the required amount of water from the ambient air before the first treatment session. It is also understood that the amount of waste liquid to be discarded corresponding to FWF in the drawings is significantly reduced. In the above numerical example, 18L of waste liquid is reduced to 0.25×14.5 + 0.1×3.5 ≈ 4L. Obviously, WSS12 facilitates the disposal of waste liquid generated by the dialysis system.

[0101] Figure 4 is a block diagram of an exemplary DHU subsystem 20 implemented as an integrated device (hot water supply device). The DHU subsystem 20 includes a water extraction unit 210 configured to receive and process an incoming (inflow) gas stream (DIA) and change the phase state of at least a portion of the contained moisture from gas to liquid. Thereby, liquid water (EW) is extracted from the incoming gas stream (DIA), and an outflow gas stream (DOA) with reduced humidity is generated.

[0102] In some embodiments, the water extraction unit 210 is configured to extract EW by directly condensing the moisture in DIA by cooling the gas below its dew point, sometimes at high pressure. For example, the water extraction unit 210 can include a conventional cooling element such as an evaporator coil configured to cool DIA to condense water. In these embodiments, box 210A represents the cooling element. This type of water extraction is mainly effective for DIA with a high RH, such as exceeding about 40%. Generally, the purity of EW obtained by this technique depends on the quality of DIA.

[0103] In some embodiments, the water extraction unit 210 is instead configured to extract EW by using a desiccant. In these embodiments, box 210A represents the desiccant. The desiccant is a hygroscopic material configured to interact with DIA. During this interaction, the desiccant absorbs and / or adsorbs water molecules present in DIA. The water extraction unit 210 is configured to treat the desiccant 210A to release water molecules, for example, by one or more of heating, changing the water vapor pressure, or UV irradiation. The released water molecules are then collected to form EW. This type of water extraction is also effective for DIA having a low RH of 20% or less. Generally, the quality of the EW obtained by this technique depends on the desiccant, particularly its selectivity for water.

[0104] The DHU subsystem 20 in FIG. 4 includes a gas inlet 202A, a gas outlet 202B, and a water outlet 202C. The gas inlet 202A opens into a gas inlet channel 201 that extends to the water extraction unit 210. A filter 202 is disposed within the gas inlet channel 201 to remove particulate matter such as debris, dust, and optionally volatile organic components, carbon, sub-micrometer particles, etc. A pump device 203, such as a fan, is disposed downstream of the filter 202 to generate and drive a gas flow through the water extraction unit 210. A humidity sensor 204 is disposed within the gas inlet channel 201 to sense the inlet humidity Hdi of the DIA. The gas outlet 202B opens into a gas outlet channel 205 that extends from the water extraction unit 210. A humidity sensor 206 is disposed within the gas outlet channel 205 to sense the outlet humidity Hdo of the DOA. The water outlet 202C opens into a water outlet channel 207 that extends from the water extraction unit 210. A flow controller 208 is disposed in the water outlet channel 207 to control the flow of EW from the water extraction unit 210. The flow controller 208 may include, for example, a valve and / or a pump device. A local controller (“control unit”) 209 is configured to generate control signals for the fan 203, the flow controller 208, and the water extraction unit 210 based on sensor signals from the humidity sensors 204, 206, to achieve one or more target values given by a control signal C3 from the main controller (60 in FIG. 2). For example, the control signal C3 may specify a target value for the flow rate of EW (“EW generation rate”) and / or a target value for the outlet humidity Hdo. The target value for the EW generation rate may be set to ensure that a sufficient amount of EW is extracted over a predetermined period, such as 24 hours. The local control unit 209 may, for example, control the flow rate of the DIA based on Hdi to achieve the target value of the EW generation rate. Alternatively or additionally, the local control unit 209 can control the flow rate of the DIA based on Hdi to achieve the target value of Hdo.

[0105] The water extraction unit 210 can generate EW having a purity sufficient for use in dialysis. Specifically, it has been found that substantial purification of EW can be achieved by using a desiccant having a high selectivity for water. High selectivity means that the desiccant is tuned to adsorb and / or absorb water molecules rather than other molecules that may be present in the DIA.

[0106] In some embodiments, the water extraction unit 210 is configured to generate EW having a conductivity of less than 10 μS / cm, preferably less than 5 μS / cm or 1 μS / cm. As understood from the above, this can be achieved by using a desiccant having a high selectivity for water. Under certain circumstances, the DHU subsystem 20 operating by direct condensation can also generate EW of sufficient purity.

[0107] In some embodiments, the desiccant is an ionic or covalent porous solid including, but not limited to, metal-organic and organic porous framework materials, zeolites, organic ion solids, inorganic ion solids, organic molecular solids, or inorganic molecular solids, or any combination thereof. The desiccant can be used in pure single-phase form, as a composition of different active chemicals, and / or in combination with performance-enhancing additives that modulate its properties. The performance-enhancing additives can include materials having high thermal conductivity and molar water absorption. The active compounds can be used in the form of powders, extrudates, molded bodies, compressed pellets, pure or composite films, or sintered bodies. In some embodiments, the water capture material includes an active compound such as a metal-organic framework (MOF). A MOF is a porous material having repeating secondary building units (SBUs) linked to organic ligands. In some variations, the SBU may include one or more metals or metal-containing complexes. In other variations, the organic ligand has acid and / or amine functional groups. In any variation, the organic ligand has a carboxylic acid group. Any MOF capable of adsorbing and desorbing water can be used in the systems provided herein. In some embodiments, MOF-303 is used as the desiccant. MOF-303 has the structure of Al(OH)(HPDC), where HPDC represents 1H-pyrazole-3,5-dicarboxylate. Other possible MOFs for use as desiccants include, for example, MOF-801, MOF-841, and MIL-160. Combinations of MOFs can also be used as desiccants. Further examples and details of implementation are described in the articles “Metal-Organic Frameworks for Water Harvesting from Air” by Kalmutzki et al. published in Adv. Mater. 2018, 30, 1704304, and “Practical water production from desert air” by Fathieh et al. published in Sci. Adv. 2018, Vol. 8, Issue 6, which are incorporated herein by reference.

[0108] Figures 5A - 5B show an embodiment of the WSS12 in which the HU subsystem 30 includes a recirculation path 34 that includes the supply side 31A of the MD unit 31. Thereby, the recirculation path 34 is arranged (configured) such that waste liquid is recirculated at the supply side 31A of the MD unit 31 while gas passes through the extraction side 31B. By recirculating the WF, the amount of water vapor transmitted through the membrane 31' can be increased for a given WF flow rate at the supply side 31A. Those skilled in the art understand that in order to transmit a given amount of water through the membrane 31' from the WF, the WF flow rate needs to be significantly lower when the WF passes through the supply side 31A only once compared to when the WF is circulated multiple times at the supply side 31A. A low WF flow rate can increase the risk of membrane fouling. Therefore, providing the recirculation path 34 can improve the efficiency of the HU subsystem 30 and reduce the need for service and repair.

[0109] In the embodiment of FIGS. 5A - 5B, a waste liquid pump is provided in the recirculation path 34, and the waste liquid pump is operable to circulate the WF on the recirculation path 34 and thus through the supply side 31A of the MD unit 31. The waste liquid pump corresponds to pump P1 in FIG. 2 and is denoted by the same reference numeral. Further, similar to FIG. 2, a WF sensor 33 is arranged downstream of the supply side 31A and is configured to generate a signal S1. Similar to the embodiment of FIG. 2, the operation of pump 1 can be controlled based on the signal S1 from the WF sensor 33.

[0110] The embodiments of FIGS. 5A - 5B also include an improved heating device (see 32 in FIG. 2) that includes a combination of an electric heater 32' and a heat transfer device 32''. The heat transfer device 32'' is configured to transfer thermal energy from the humid gas flow generated by the MD unit 31 to the WF upstream of the supply side 31A of the MD unit 31. The heat transfer device 32'' may include a heat exchanger and / or a heat pump. Such a heat pump is operated to transfer thermal energy by the use of a refrigeration cycle, as is well known in the art. Alternatively or additionally, the heat transfer device 32'' may be configured to transfer thermal energy from the water extraction unit 210 within the DHU subsystem 20, taking into account that thermal energy is released when water vapor is converted to liquid water.

[0111] In the embodiments of FIGS. 5A - 5B, the DHU subsystem 20 is fluidly connected to receive humidified gas from the MD unit 31 on the first fluid path 23' and to provide dehumidified gas to the MD unit 31 on the second fluid path 23'. The fluid path 26 for EW extends from the DHU subsystem 20 to the EW container 52, from where EW is provided to a dialysis system (not shown). An air outlet 24 is provided in the first fluid path 23', and an air inlet 25 is provided in the second fluid path 23'. Each on - off valve (on / off valve) V1, V2 is arranged to selectively open and close the air outlet 24 and the air inlet 25. Another on - off valve V3 is arranged in the second fluid path 23'' downstream of the air outlet 24 to selectively open and close the second fluid path 23''. Functionally, valves V1 - V3 correspond to valves V', V'' in FIG. 2 and define a valve configuration (valve arrangement) for switching WSS12 between the HDH mode and the DH mode. In the HDH mode, valves V1, V2 are closed and valve V3 is open. In the DH mode, valves V1, V2 are open and valve V3 is closed. Assuming that the DHU subsystem 20 includes a gas pump device (see fan 203 in FIG. 4), air is driven through the DHU subsystem 20 in both the HDH mode and the DH mode. In the DH mode, as indicated by the dashed arrow, EIA flows in through the air inlet 25 and EOA is discharged through the air outlet 24.

[0112] The operation of the HU subsystem 30 in FIGS. 5A - 5B is optionally controlled by the main controller 60 (FIG. 2) via a local controller 39 (the "control unit") as shown in FIGS. 5A - 5B. The local controller 39 may be configured to generate control signals for the pump P1, the heater 32', the heat transfer device 32'', and the valves and / or pumps included.

[0113] Here, referring particularly to the embodiment of FIG. 5A, the HU subsystem 30 is configured for batch processing of WF. The way the batch process operates is to introduce a batch of WF into path 34, operate the waste liquid pump P1 to circulate the WF on path 34, and thus pass through the supply side 31A, while passing the gas through the draw side 31B. The circulation of WF continues until the WF reaches a predetermined state. The predetermined state is achieved when the concentration-related characteristic measured by the WF sensor 33 reaches a limit value. This limit value determines the "water recovery rate" of the HU subsystem 30, which indicates the proportion of water in the WF available for transfer through the membrane 31. In the predetermined state, the waste liquid forms "final waste liquid" (FWF) that is at least partially discharged from path 34. The amount of WF processed in each batch is given by the volume of the recirculation path 34. In the embodiment of FIG. 5A, a flow-through container 34A is included in the recirculation 34 to enable processing of large amounts of WF. The HU subsystem 30 of FIG. 5A further includes various flow controllers V4 - V7, such as on-off valves, arranged to enable filling and draining of the recirculation path 34. Further, in the example shown, P1 is a bidirectional pump used for filling, circulation, and draining. To fill path 34, V4 is closed, V5 is opened, and P1 is operated to pump WF into path 34 from the inlet line 35 that may extend to the WF container (51 in FIG. 2) towards the container 34A. When a sufficient amount of WF has entered path 34, V4 is opened, V5 is closed, and P1 is reversed to circulate the WF through the container 34A and the MD unit 31 within path 34. The amount of WF entering path 34 can be monitored by any suitable means, such as a level sensor in the container 34A, a pressure sensor in path 34, a flow meter, or volumetric pumping by P1. To add tap water (TW), V7 is intermittently opened so that P1 draws TW from the inlet line 37 that may extend to the TW container (53 in FIG. 2). When the WF reaches the predetermined state, V6 is opened and V4 is closed, and as a result, P1 pumps the FWF into the outlet line 36 that can extend to an FWF container (not shown) or the drain.In a modified example, P1 is a one-way pump operable to circulate WF on path 34, and WF is pumped into the path by a separate pump disposed in inlet line 35. The separate pump may be disposed downstream of the WF container (51 in FIG. 2). If no WF container is installed, the separate pump may be part of the dialysis system.

[0114] In the embodiment of FIG. 5B, the HU subsystem 30 is configured for continuous processing of WF. The method of operating the continuous process is, at the same time, to put a first amount of WF into path 34 and discharge a second amount of processed WF from path 34. The first amount and the second amount are jointly controlled such that the first amount replaces the second amount and the amount of water transmitted through membrane 31' from supply side 31A to draw side 31B. In other words, the difference between the first amount and the second amount is set to be substantially equal to the amount of water exiting path 34 in MD unit 31. Various flow controllers are arranged to enable filling and draining of path 34. In the example of FIG. 5B, the flow controllers include pump P2 in inlet line 35 that may extend to the WF container (51 in FIG. 2), pump P3 in outlet line 36 that may extend to an FWF container (not shown) or a drain, and on / off valve V7 in inlet line 37 that may extend to the TW container (53 in FIG. 2). In the HU subsystem 30 of FIG. 5B, P1 is operated to circulate WF within path 34, while P2 is operated to supply WF, P3 is operated to remove WF, while essentially maintaining a constant amount of fluid within path 34. Pumps P2 and P3 may be jointly controlled in any suitable manner, for example, by volumetrically balancing the flow rates through paths 26, 35, 36 or by maintaining a stable fluid pressure within path 34 measured by a pressure sensor. V7 is opened intermittently to add tap water.

[0115] The subsystems for batch processing and continuous processing differ in both structure and function, but both operate based on signal S1. The first flow controller introduces a first amount of WF into the recirculation path 34, and the second flow controller discharges a second amount of the processed WF from the recirculation path 34, where the processed WF contains the WF that has been recirculated at least once through the supply side 31A of the MD unit 31. In FIG. 5A, the first flow controller corresponds to the combination of V4 and V5, and the second flow controller corresponds to the combination of V4 and V6. In FIG. 5B, the first flow controller corresponds to P2, and the second flow controller corresponds to P3.

[0116] In the DH mode, WSS12 generates water by dehumidifying the ambient air. As described above, the DH mode can be activated (enabled) whenever the WF is not available for water extraction, for example, to close (fill) the gap between the target value and the amount of EW available for extraction from the WF. The EW generated in the DH mode is taken directly from the ambient air. If a large amount of EW is generated in a short time in the DH mode, the humidity of the ambient air may decrease to an unacceptable level. On the other hand, when the amount of EW generated in the DH mode is maximized, the amount of EW generated in the HDH mode can be reduced. Thereby, in the HDH mode, the water recovery rate can be decreased and the risk of membrane fouling can be reduced. Therefore, there is a trade-off between the risk of drying the ambient air in the DH mode and the risk of membrane fouling in the HDH mode.

[0117] In some embodiments, the WSS 12 is operated to maximize the EW generation rate in the DH mode while maintaining an acceptable humidity of the ambient air. For example, a first minimum may be defined for the humidity of the ambient air measured by the sensor 204 in FIG. 2, and the DHU subsystem 20 may be operated to generate EW so as not to fall below the first minimum. In some embodiments, the first minimum is in the range of 20 - 40% RH. In some embodiments, a second minimum is defined for the air released to the ambient (EOA) measured by the sensor 206 in FIG. 2, for example. In some embodiments, the second minimum is in the range of 0 - 20% RH. One or both of the first and second minima may be used to control the WSS 12 in the DH mode. Each minimum may be predefined for the WSS 12 or set by the user. Each minimum may be scheduled to have different values at different times, for example, considering that a user is expected to be within the threshold of the WSS 12. If it is required to exceed the minimum, the WSS 12 may be operated to reduce the air flow rate through the DHU subsystem 20 while maintaining the humidity difference between the inlet humidity (Hdi in FIG. 2) and the outlet humidity (Hdo in FIG. 2). In a variant, to exceed the minimum, the humidity difference is instead reduced and the air flow rate is maintained. In other variants, both the air flow rate and the humidity difference are adjusted.

[0118] In the HDH mode, all the water vapor entering the gas flow through the membrane 31' can be recovered within the DHU subsystem 20. Thus, in some embodiments, the humidification rate in the HU subsystem 30 is equal to the dehumidification rate in the DHU subsystem 20, which is equal to the EW generation rate. Depending on the situation, for example, to avoid EW shortage, the WSS 12 can be operated in the HDH mode to increase the EW generation rate far above the average target. In such a case, one of the subsystems 20, 30 limits the EW generation rate.

[0119] In some embodiments of the HDH mode, the DHU subsystem 20 functions as a master. This means that the required combination of the flow rate and the moisture content of the incoming gas stream (DIA) is determined to enable the DHU subsystem 20 to reach the target value of the EW production rate. Then, the HU subsystem 30 is operated to extract water from the waste liquid so as to achieve the moisture content measured by the sensor 204 and provided, for example, as the inlet humidity (Hdi in FIG. 2), while the fan 203 is optionally operated to generate the required gas flow rate based on feedback from a flow meter (not shown). If the required combination of the moisture content and the gas flow rate cannot be satisfied, the HU subsystem 30 can be operated to maximize its water transfer rate through the membrane 31', which corresponds to maximizing the amount of water vapor provided to the DHU subsystem 20 per unit time. The water transfer rate can be adjusted by changing the inlet temperature and / or the flow rate of the waste liquid on the supply side 31A, by changing the inlet temperature and / or the flow rate of the gas on the draw side 31B, by changing the composition of the waste liquid (e.g., used dialysis fluid or maintenance fluid), by changing the water recovery rate, or by any combination thereof.

[0120] The inlet temperature of the waste liquid on the supply side 31A can be achieved by operating the heat transfer device 32'' to transfer heat from the gas exiting from the draw side 31B to the WF flowing into the supply side 31A. If it is necessary to achieve the required inlet temperature, the electric heater 32' can optionally be operated to increase the WF temperature based on feedback from a temperature sensor.

[0121] WSS12 can also be operated to reduce membrane fouling within the MD unit 31. This can be achieved by increasing the WF flow rate through the feed side 31A, by pre-diluting the WF with TW or low-concentration WF (if available) to reduce the concentration of scaling compounds, or by alternately supplying WF and TF (or high-concentration and low-concentration WF) through the feed side 31A to increase the shear force near the surface. The risk of fouling (contamination) generally increases with the water recovery rate. In some embodiments, WSS12 is operated at a water recovery rate that provides an acceptable trade-off between the fouling risk and water extraction.

[0122] The following is a non-limiting example of the use of a combination of a WSS12 and an APD system that is operated to perform treatment sessions at night. The starting point of the example is the night before the session. At the starting point, the WF may or may not be available to the WSS12. However, it is assumed that the EW container 52 within the WSS12 holds enough water at the starting point to produce at least the first two fill volumes of PD fluid during the session. For example, the amount of water available may be between 4 and 10 L. During the preparation (preparation), initial filling phase, and initial retention phase of the PD fluid, the WSS12 is operated to produce EW in DH mode if the WF is not available and in HDH mode if the WF is available. After the first drain phase, for the remainder of the session, the WSS12 operates in HDH mode to produce EW from the used PD fluid obtained in each drain phase. The produced EW is collected in the EW container 52, and the treated waste fluid (FWF) is discarded in a disposable container. Depending on the EW production rate with respect to the production rate of the used PD fluid during the session, the used PD fluid may be stored in the WF container 51 for subsequent processing. The WSS12 can be intermittently switched to DH mode to utilize water in the ambient air without significantly affecting the ambient humidity. After the last drain phase, the WSS12 receives maintenance fluid from the APD system and operates in HDH mode to produce EW from the used PD fluid from the last drain phase, the maintenance fluid, and any stored WF. During the day (midday), the WSS12 may be switched between HDH mode and DH mode, for example, based on the humidity of the ambient air. If the presence of the user is detected during the day, for example, if the user interacts with the APD system, the user may be prompted to supply TW to the WSS12 if it is considered necessary based on the available amounts of EW and WF, the humidity of the ambient air, the operating history of the APD system and / or the WSS12, or any combination thereof.

[0123] It should be understood that WSS12 can be controlled based on either relative humidity or absolute humidity. For example, by also measuring temperature, the measured relative humidity can be converted to absolute humidity.

[0124] The subject matter of the present disclosure has been described in connection with what is presently considered to be the most practical embodiments, but the subject matter of the present disclosure should not be limited to the disclosed embodiments. Rather, it is intended to cover various modifications and equivalents included within the spirit and scope of the appended claims.

[0125] Furthermore, although the operations are shown in the drawings in a particular order, it should not be understood that such operations are required to be performed in the particular order shown, or in a sequential order, or that all of the shown operations are to be performed, in order to achieve desirable results.

Claims

1. A water supply system for a dialysis system (10), A first subsystem (20) is configured to convert a first gas flow (DIA) into a second gas flow (DOA) by extracting liquid water (EW) from the first gas flow (DIA), and to provide the liquid water (EW) for use by the dialysis system (10). A second subsystem (30) is configured to process the second gas flow (DOA) using wastewater from the dialysis system (10) to generate the first gas flow (DIA) having increased humidity compared to the second gas flow (DOA), The system includes a control device (60) configured to operate the first and second subsystems (20, 30) together to generate a target amount of liquid water (EW), The water supply system comprises a membrane distillation (MD) unit (31) defining a supply side (31A) and a draw side (31B) separated by a hydrophobic membrane (31'), wherein the MD unit (31) receives the wastewater (WF) at an inlet (31Ai) of the supply side (31A) and receives the second gas flow (DOA) at an inlet (31Bi) of the draw side (31B), and the MD unit (30) is configured to generate the first gas flow (DIA) by transferring water vapor from the wastewater (WF) to the second gas flow (DOA) through the hydrophobic membrane (31') via the difference in partial water vapor pressure between the supply side (31A) and the draw side (31B).

2. The water supply system according to claim 1, wherein the control device (60) is configured to selectively operate the first subsystem (20) to acquire at least a portion of the first gas flow (DIA) from the ambient air and to supply at least a portion of the second gas flow (DOA) to the ambient air.

3. The water supply system according to claim 1 or 2, wherein the control device (60) is configured to selectively switch the system between a first mode in which the first and second gas flows (DIA, DOA) are transmitted in a closed loop between the first and second subsystems (20, 30) and a second mode in which the transmission is blocked and the first subsystem (20) is operated to obtain the first gas flow (DIA) from the ambient air and provide the second gas flow (DOA) to the ambient air.

4. The water supply system according to claim 3, wherein the control device (60) is configured to switch between the first and second modes based on at least one of the current moisture content of the ambient air, the availability of wastewater (WF), the availability of liquid water (EW), or a time schedule.

5. The water supply system according to claim 1 or 2, wherein the second subsystem (30) is located upstream of the inlet (31Ai) of the supply side (31A) of the MD unit (31) and further comprises a heating device (32) that is operable to heat the wastewater (WF).

6. The water supply system according to claim 5, wherein the heating device (32) comprises a heat transfer device (32'') configured to transfer thermal energy from the first gas flow (DIA) generated by the MD unit (31) to the waste liquid (WF).

7. The water supply system according to claim 1 or 2, wherein the second subsystem (30) is located downstream of the outlet (31Ao) of the supply side (31A) of the MD unit (31) and further comprises a WF sensor (33) that provides a measurement signal (S1) indicating the concentration-related characteristics of the waste liquid (WF), and the control device (60) is configured to operate the second subsystem (30) based on the measurement signal (S1).

8. The water supply system according to claim 7, wherein the concentration-related characteristics include concentration, density, conductivity, color, transparency, or refractive index.

9. The water supply system according to claim 7, wherein the second subsystem (30) defines a recirculation path (34) including the supply side (31A) of the MD unit (31), the second subsystem (30) includes a pump device (P1) in the recirculation path (34), and the control device (60) is configured to operate the pump device (P1) based on the measurement signal (S1) to recirculate the waste liquid (WF) through the supply side (31A) of the MD unit (31).

10. The water supply system according to claim 9, wherein the control device (60) is further configured to selectively operate a first flow controller (V5, P2) based on the measurement signal (S1) to introduce a first amount of wastewater (WF) into the recirculation path (34), and to operate a second flow controller (V6, P3) to discharge a second amount of treated wastewater (FWF) from the recirculation path (34), the treated wastewater comprising wastewater that has been recirculated at least once through the supply side (31A) of the MD unit (31).

11. The water supply system according to claim 10, wherein the control device (60) is configured to sequentially operate the first flow controller (V5) to introduce the first amount into the recirculation path (34), operate the pump device (P1) to circulate at least the first amount through the supply side (31A) of the MD unit (31), and operate the second flow controller (V6) to discharge the second amount from the recirculation path (34).

12. The water supply system according to claim 10, wherein the control device (60) is configured to simultaneously operate the first flow controller (P2) to introduce the first amount into the recirculation path (34) and operate the second flow controller (P3) to discharge the second amount from the recirculation path (34), such that the difference between the first and second amounts is substantially equal to the third amount of water transmitted to the second gas flow (DOA) through the hydrophobic membrane (31').

13. The water supply system according to claim 9, wherein the control device (60) is configured to selectively operate the supply device (53, V7) to supply tap water to the recirculation path (34), and to operate the pump device (P1) to circulate the tap water (TW) through the supply side (31A) of the MD unit (31).

14. A device comprising: a water supply system (12) according to claim 1 or 2; and a dialysis system (10) configured to receive a medical fluid (MF) for dialysis treatment performed by a dialysis system (10) and to generate wastewater (WF) at least partially generated from the medical fluid (MF) during the dialysis treatment, wherein the dialysis system (10) is fluidly connected to transmit the wastewater (WF) to the water supply system (12).

15. A computer-assisted method for providing water for use in a dialysis system, The first subsystem is operated to convert the first gas flow into a second gas flow by extracting liquid water from the first gas flow (302), (304) Providing the liquid water for use by the dialysis system, The system includes (303) operating the second subsystem in coordination with the first subsystem to process the second gas flow using wastewater from the dialysis system and to generate the first gas flow having increased humidity compared to the second gas flow, The method comprises, operating the second subsystem (303), supplying the waste liquid at the supply side inlet of a membrane distillation (MD) unit (303A), and supplying the second gas flow at the draw-side inlet of the MD unit (303B), wherein the draw-side is separated from the supply side by a hydrophobic membrane, and the MD unit is configured to generate the first gas flow by transferring water vapor from the waste liquid to the second gas flow through the hydrophobic membrane via a partial water vapor pressure difference between the supply side and the draw-side.

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